1 package org.apache.commons.graph.model;
2
3 /*
4 * Licensed to the Apache Software Foundation (ASF) under one
5 * or more contributor license agreements. See the NOTICE file
6 * distributed with this work for additional information
7 * regarding copyright ownership. The ASF licenses this file
8 * to you under the Apache License, Version 2.0 (the
9 * "License"); you may not use this file except in compliance
10 * with the License. You may obtain a copy of the License at
11 *
12 * http://www.apache.org/licenses/LICENSE-2.0
13 *
14 * Unless required by applicable law or agreed to in writing,
15 * software distributed under the License is distributed on an
16 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
17 * KIND, either express or implied. See the License for the
18 * specific language governing permissions and limitations
19 * under the License.
20 */
21
22 import static java.lang.reflect.Proxy.newProxyInstance;
23
24 import java.lang.reflect.InvocationHandler;
25 import java.lang.reflect.Method;
26
27 import org.apache.commons.graph.Edge;
28 import org.apache.commons.graph.Vertex;
29
30 /**
31 * Simple {@link Edge} Proxy that inverts head/tail for undirectedGraph implementations.
32 *
33 * @param <V> the Graph vertices type
34 */
35 final class InvertedEdgeAdapter<V extends Vertex>
36 implements Edge<V>, InvocationHandler
37 {
38
39 /**
40 * Creates a new inverted {@link Edge}.
41 *
42 * @param <V> the Graph vertices type
43 * @param <E> the Graph edges type
44 * @param edge the edge has to be inverted
45 * @return
46 */
47 public static <V extends Vertex, E extends Edge<V>> E invertHeadAndTail( E edge )
48 {
49 @SuppressWarnings( "unchecked" ) // type driven by input
50 E edgeProxy = (E) newProxyInstance( edge.getClass().getClassLoader(), edge.getClass().getInterfaces(),
51 new InvertedEdgeAdapter<V>( edge ) );
52 return edgeProxy;
53 }
54
55 private final Edge<V> adapted;
56
57 /**
58 * Creates a new inverted {@link Edge}, wrapping a default one.
59 *
60 * @param adapted the wrapped Edge
61 */
62 private InvertedEdgeAdapter( Edge<V> adapted )
63 {
64 this.adapted = adapted;
65 }
66
67 /**
68 * {@inheritDoc}
69 */
70 public V getHead()
71 {
72 return adapted.getTail();
73 }
74
75 /**
76 * {@inheritDoc}
77 */
78 public V getTail()
79 {
80 return adapted.getHead();
81 }
82
83 /**
84 * {@inheritDoc}
85 */
86 public Object invoke( Object proxy, Method method, Object[] args )
87 throws Throwable
88 {
89 try
90 {
91 return method.invoke( this, args );
92 }
93 catch ( Throwable t )
94 {
95 return method.invoke( adapted, args );
96 }
97 }
98
99 }